1. Field of the Invention
The present invention relates to a fluid-sealed anti-vibration device which is used in an engine mounting and the like in which a cylindrical bushing and a cone-shaped mounting are integrally provided and dynamic characteristics are improved in a cylindrical bushing.
2. Description of the Prior Art
A cone-shaped mounting is known in the prior art, in which a first connecting member secured to a vibration generating side, a second connecting member secured to a vibration receiving side, and a substantially cone-shaped elastic body section for connecting the first and second connecting members are provided. A fluid chamber is provided inside the elastic body section which forms a part of the elastic wall of the fluid chamber. The fluid chamber is divided into a main fluid chamber and a sub-fluid chamber by a partition member and a first orifice is provided for communicating with both fluid chambers. A cylindrical bushing is also known in the prior art in which inner and outer tubes of a cylindrical shape are connected by an elastic member and a plurality of fluid chambers divided by the elastic member in the circumferential direction is provided. An orifice is arranged to communicate with these fluid chambers.
The present applicant has also filed another patent application (U.S. patent application Ser. No. 09/749,829) concerning a fluid-sealed anti-vibration device similar to the device shown in FIG. 1 and FIG. 2 of the present application. In this application, a cone-shaped mounting section is integrally provided by using an elastic wall which forms a part of a fluid chamber of a cylindrical bushing section and an elastic body section in common. By this integration, the vibrations in the biaxial directions which meet at right angles can be absorbed by the cylindrical bushing section and the vibrations in the direction perpendicular to these can be absorbed by the cone-shaped mounting section. Accordingly, all the vibrations in the triaxial directions which meet at right angles can be absorbed by a single device. In the following description, the vertical direction (the front and rear direction when a car body is installed) and the lateral direction (the lateral direction when the car body is installed) in a condition shown by FIG. 1, and the vertical direction in FIG. 2 (the vertical direction when the car body is installed) are referred to as the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively.
As described above, when the cylindrical bushing section and the con-shaped mounting section are integrally provided, each is provided with a membrane resonance section. Accordingly, as an overall fluid-sealed anti-vibration device, the dynamic spring characteristics in the medium to high frequency range have been determined by coupling each membrane resonance in the cylindrical bushing section and the cone-shaped mounting section. As a result, it is difficult to realize a low dynamic spring effect in a wider range and to form the minimum value of the dynamic spring constant in a specified frequency. It is therefore desirable to make this possible. (Hereinafter the minimum value of the dynamic spring constant is referred to as xe2x80x9ca dynamic spring bottomxe2x80x9d. Likewise, the maximum value of the dynamic spring constant is referred to as xe2x80x9ca dynamic spring peakxe2x80x9d.)
It is therefore a first object of the present invention to realize such a demand and it is a second object to improve dynamic characteristics such as lowering a dynamic spring constant in an optional frequency. The medium to high frequency bands here mean those between about 200 and 1,000 Hz.
In the cylindrical bushing section 2, the elastic member used therein acts as a rubber spring has spring values, each being peculiar to the front and rear direction and the lateral direction. However, when the recessed sections, which is a space opened to the atmosphere, are provided between the neighboring fluid chambers in a circumferential direction, the spring value is reduced in the direction in which the recessed sections are provided. Accordingly, to improve a comfortable car riding, it is necessary to increase the spring values in this direction. For the increase of spring values, it is also considered that the elastic partition wall, which is a partition wall between the recessed section and the fluid chambers, is thickened to raise the rigidity. However, in a case where the recessed sections are disposed in the lateral direction and the liquid chambers are disposed in the front and rear direction, since the elastic partition wall is elastically deformed relative to the input of vibrations in the front and rear direction, it is required to make the capacity of the side fluid chambers variable. Accordingly, it is not possible to raise the rigidity without limitation. It is therefore required to have such a membrane construction as to raise the rigidity relative to only the vibrations in the lateral direction.
It is therefore a third object of the present invention to realize such a demand.
To attain the above-mentioned first object, according to a first invention of the present invention, a fluid-sealed anti-vibration device is provided, which comprises a cone-shaped mounting section and a cylindrical bushing section, the cone-shaped mounting section being provided with a first connecting member secured to either of a vibration generating side or a vibration receiving side, a second connecting member secured to the other side, a substantially cone-shaped elastic body section for connecting the first and second connecting members, a fluid chamber of which part of an elastic wall is the elastic body section and of which the inside is divided into a main fluid chamber and a sub-fluid chamber by a partition member, and a first orifice for communicating with the main fluid chamber and the sub-fluid chamber, the cylindrical bushing section being provided with a plurality of side fluid chambers which are provided in the circumferential direction at predetermined intervals on the outer circumstance of the elastic body section and of which part of an elastic wall is the elastic body section, and a second orifice for communicating with each side fluid chamber, characterized in that the cone-shaped mounting section and the cylindrical bushing section are caused to generate a membrane resonance in each different natural frequency, and the maximum value or the minimum value of a dynamic spring constant generated by the natural membrane resonance in the cone-shaped mounting section and the maximum value or the minimum value of the dynamic spring constant generated by the natural membrane resonance in the cylindrical bushing section are coupled to interfere with each other, thereby providing low dynamic spring characteristics.
Each natural membrane resonance in the cone-shaped mounting section and the cylindrical bushing section is a membrane resonance with the natural resonant frequency and the dynamic spring characteristics which can be obtained by filling and sealing a fluid in a fluid chamber on either side of the cone-shaped mounting section or the cylindrical bushing section, and by measuring the dynamic spring characteristics.
At this time, the fluid-sealed anti-vibration device may be provided, wherein the cylindrical bushing section forms the maximum value of the dynamic spring constant in the natural frequency by a plurality of membrane resonances and also forms the minimum value of the dynamic spring constant on a higher frequency side than the natural frequency, while the cone-shaped mounting section generates a membrane resonance which forms the minimum value of the dynamic spring constant near and on a frequency side lower than the natural frequency which gives the maximum value.
Also, the fluid-sealed anti-vibration device may be provided, wherein the cylindrical bushing section forms the maximum value of the dynamic spring constant by the natural membrane resonance, and the cone-shaped mounting section also forms the minimum value of the dynamic spring constant by the natural membrane resonance, wherein there is the natural frequency where the minimum value on the mounting section side is formed near and on a frequency side higher than the natural frequency where the maximum value on the bushing section side is formed.
Further, an elastic membrane for absorbing the fluctuations in the internal pressure in the main fluid chamber may be provided, facing the main fluid chamber of the cone-shaped mounting section.
Furthermore, a disc member adapted to move together with the first connecting member may be provided within the main fluid chamber of the cone-shaped mounting section.
In order to attain the above-mentioned second object, a second invention of a fluid-sealed anti-vibration device of this patent application comprises a first mounting member that is mounted on either a vibration generating side or a vibration receiving side, a second mounting member that is mounted on the other side and encloses the first mounting member in a nearly cylindrical state, an elastic partition wall provided for connecting these first and second mounting members and dividing the inside of the device into plural chambers, and a cylindrical bushing communicating with these fluid chambers through orifice passages, wherein three pairs of the fluid chambers are provided and three kinds of orifice passages are provided for communicating with each pair of fluid chambers through an orifice passage.
At this time, one of said three kinds of orifice passages can be made as a damping orifice passage and the liquid column resonance frequency of the other two orifices is set near the liquid column resonance frequency of the damping orifice passage.
Also, one of said three kinds orifice passages can be made as a damping orifice passage, another orifice passage as an idle orifice passage and the remaining orifice passage is set at a liquid column resonance frequency where the anti-resonance frequency of the idle orifice passage becomes maximum.
Further, the liquid column resonance frequency of one of three kinds of orifice passages having the largest rate of fluid flow out of said three kinds of orifice passages can be set lower than the liquid column resonance frequency of other orifice passages.
Furthermore, the liquid column resonance frequency of one of said three kinds of orifice passages having the largest rate of fluid flow out of three kinds of orifice passages can be set higher than the liquid column resonance frequencies of the other orifice passages.
To attain the above-mentioned third object, according to a third invention of the present invention, a fluid-sealed anti-vibration device having a cylindrical bushing section is provided, in which the cylindrical bushing section comprises a first connecting member secured to either of a vibration generating side or a vibration receiving side, a second connecting member secured to the other side and enclosing the periphery of the first connecting member in a substantially cylindrical shape, and an elastic partition wall for connecting the first and second connecting members, wherein the inside of the cylindrical bushing section is divided by the elastic partition wall into a plurality of fluid chambers, and an orifice is provided to communicate with each fluid chamber, characterized in that by press-fitting the elastic partition wall to the first or second connecting member side, the elastic partition wall is compressed by the first or second connecting member to adjust a spring ratio in the direction for connecting the first and second connecting members and in the direction substantially perpendicular to that direction.
To obtain the above-mentioned third object according to a forth invention of the present application, a fluid-sealed anti-vibration device having a cone-shaped mounting section and a cylindrical bushing section is provided, in which the cone-shaped mounting section is provided with a first connecting member secured to either of a vibration generating side or a vibration receiving side, a second connecting member secured to the other side, and a substantially cone-shaped elastic body member for connecting the first and second connecting members, wherein a fluid chamber is provided of which part of an elastic wall is the elastic body member and of which the inside is divided by a partition member into a main fluid chamber and a sub-fluid chamber, and a first orifice is provided to communicate with the main fluid chamber and the sub-fluid chamber, and the cylindrical bushing section is provided with a plurality of side fluid chambers on the outer periphery of the elastic body member which is used in common with a part of the elastic wall of the fluid chambers, in the circumferential direction at a predetermined interval, wherein a second orifice is provided to communicate with each side fluid chamber, characterized in that the cylindrical bushing section and the cone-shaped mounting section are integrally provided, and the side fluid chambers are divided by an elastic partition wall which connects the first and second connecting members, wherein by press-fitting the elastic partition wall to the first or second connecting member side, the elastic partition wall is compressed by the first or second connecting member to adjust a spring ratio in the direction for connecting the first and second connecting members and in the direction substantially perpendicular to that direction.
In the above-mentioned third and fourth invention, the fluid-sealed anti-vibration device according to the first or second invention can be provided, wherein a seat section to which the elastic partition wall is press-fitted is provided with a projecting section which engages a press-fitting end of the elastic partition wall, and there is provided a predetermined space between the projecting section and the elastic partition wall.
According to the first invention, the maximum value or the minimum value of the dynamic spring constant generated by the nature membrane resonance in the cone-shaped mounting section and the maximum value or the minimum value of the dynamic spring constant generated by the natural membrane resonance in the cylindrical bushing section are coupled to interfere with each other. Accordingly, the dynamic spring peak generated by the natural membrane resonance in the cylindrical bushing section or the cone-shaped mounting section is lowered by the dynamic spring bottom generated by the natural membrane resonance on the other side. As a result, a low dynamic spring effect can be realized in a wider frequency range, from the medium to high frequency.
At this time, when the cylindrical bushing section is provided with a plurality of membrane resonant sections, wherein each forms the dynamic spring peak in the specified frequency and the dynamic spring bottom on the frequency side higher than the specified frequency. Accordingly, when the membrane resonance in the cone-shaped mounting section forms the dynamic spring bottom on the frequency side lower than the specified frequency in the dynamic spring peak, the dynamic spring peak on the cylindrical bushing section side is lowered. In this case, since the dynamic spring peak is generated on the frequency side lower than the dynamic spring bottom in the cylindrical bushing section, the low dynamic spring is realized in a wider range of frequencies.
Also, when the dynamic spring peak by the natural membrane resonance in the cylindrical bushing section is generated on the frequency side lower than the dynamic spring bottom by the natural membrane resonance in the cone-shaped mounting section, the dynamic spring peak in the cylindrical bushing section is lowered by the dynamic spring bottom by the membrane resonance in the cone-shaped mounting section to realize the low dynamic spring effect.
The membrane resonance in the cylindrical bushing section having the dynamic spring peak is generated on the lower frequency side sooner than the membrane resonance on the side of the cone-shaped mounting section having the dynamic spring bottom, and the membrane resonance in the cone-shaped mounting section is strengthened by the membrane resonant energy on the cylindrical bushing section side. As a result, the dynamic spring bottom on the cone-shaped mounting section side is amplified to allow the coupled dynamic spring characteristics to cause the dynamic spring bottom. Accordingly, it is possible to form the dynamic spring bottom in the specified frequency.
Further, when an elastic membrane for absorbing the fluctuations in the internal pressure in the main fluid chamber is provided, facing the main fluid chamber of the cone-shaped mounting section, it is possible to realize a further low dynamic spring effect over the entire spring characteristics.
Furthermore, in a case that the disc member which moves together with the first connecting member is provided within the main fluid chamber of the cone-shaped mounting section, when the disc member vibrates together with the first connecting member within the main fluid chamber, liquid column resonance is generated. When the liquid column resonance is coupled to the membrane resonance of the elastic body section, it is possible to realize a further low dynamic spring in the medium to high frequency range.
According to the second invention, as three pairs of fluid chambers and three kinds of orifice passages communicating with these passages are provided, when one of three kinds of orifice passages is provided as a damping orifice passage, another passage as an idle orifice passage and the remaining passage as an orifice passage for liquid column resonance on a high frequency side, the anti-resonance effect of the liquid column resonance of the damping orifice passage is reduced and a low dynamic spring can be realized in a wide range of frequencies.
At this time, when one of three kinds of orifice passages is provided as a damping orifice passage and the liquid column frequency of the other two passages is set near the liquid column resonance frequency of the damping orifice passage, the damping by the damping orifice can be extended to a wider range of frequencies by the liquid column resonance of the other two orifice passages and it becomes possible to realize the broad damping.
Also, when one of three kinds of orifice passages is made as a damping orifice passage, another passage is provided as an idle orifice passage, and the liquid column resonance frequency of the remaining orifice passage is set at a frequency where the anti-resonance of the idle orifice passage becomes the maximum, the anti-resonance in the idle orifice passage can be absorbed by the remaining orifice passages and it becomes possible to realize a low dynamic spring on a higher frequency side than the idle frequency.
Further, when the liquid column resonance frequency of one of three kinds of orifice passages, of which the fluid flow rate is highest is reduced to less than the liquid column resonance frequency of other orifice passages, this orifice passage becomes a damping orifice passage and the influence of anti-resonance can be made less.
Furthermore, when liquid column resonance frequency of one of three kinds of orifice passages of which the fluid flow rate is highest is made higher than the liquid column resonance frequency of the other orifice passages, the liquid column resonance is generated in the remaining orifice passage on the lower frequency side and thus, it becomes possible to realize a low dynamic spring.
According to the third invention, since the fluid-sealed anti-vibration device is provided, in which the elastic partition wall of the cylindrical bushing section is press-fitted on the first or second connecting member side, the elastic partition member is compressed by the first or second connecting member to raise the spring value in the direction for connecting the first and second connecting members (hereinafter referred to as xe2x80x9cthe Y-axis directionxe2x80x9d). As a result, when the spring in the Y-axis direction in which the spring value tends to lower is strengthened, and the direction perpendicular to the Y-axis direction is the X-axis, it is possible to easily control the spring ratio in the two axial directions perpendicular to each other.
According to the fourth invention, since the cylindrical bushing section is integrally formed with the cone-shaped mounting section, when the input direction of major vibrations in the cone-shaped mounting section is the Z-axis perpendicular to the X and Y-axes, it is possible to easily control the spring ratio in the three axial directions perpendicular to each other.
Also, in the third and fourth invention, when there is provided a space between the press-fitting section of the elastic partition wall and the projecting section provided on the seat section, when the elastic partition wall is elastically deformed, the spring value is set to increase the amount of elastic deformation for smaller vibrations. On the other hand, when the vibrations are large enough to allow the elastic partition wall to contact the projecting section, further elastic deformation is controlled to increase the spring value, wherein the spring value can be changed non-linearly.